In recent experiments, we have solubilized membranes from DBA/2 mouse spleen cells using cholate and then we have reconstituted the membranes by removing the detergent. We found that cytotoxic thymus-dependent lymphocytes (CTL) specific for the H-2d major transplantation antigen (MTA) could be formed when these reconstituted membranes were added to in vitro cultures of spleen cells from C57BL/6 mice. This project is based on the above experiments. We propose to isolate and characterize biochemically the cellular components necessary for the CTL recognition and stimulation described above. For example, we plan to determine the role of the beta-2 microglobulin in CTL stimulation. We propose to test if CTL can also be stimulated using reconstituted membranes containing xenogeneic, trinitrophenyl modified or viral antigens. If such stimulation can be observed, we propose to isolate and characterize the stimulatory materials. We propose to make reconstituted membranes containing both the proteins of the Sendai viral envelope and MTA recognized by specific CTL. We hope that these membranes can fuse with membranes of intact cells using Sendai fusion and hemagglutination proteins thereby introducing the MTA into the cells and converting the cells into ones recognized by specific CTL. We propose to study the presentation of subcellular alloantigen by macrophages for the stimulation of CTL.